DevicePolicyManagerService: Suppress one off errorprone warnings for...

DevicePolicyManagerService: Suppress one off errorprone warnings for AndroidFrameworkPendingIntentMutability

These are false positives that are just taking the flags in
as an argument and passing that over to PendingIntent methods. This
change should clear up the noise.

Bug: 170162102
Test: Errorprone builds should no longer show these as violations
Exempt-From-Owner-Approval: Trivial warning suppression
Change-Id: Ida7237f60b2c8ab6dae6426d01a17fcfd67e2436